DTV receiving system and method of processing broadcast data therein

1. A receiving system, comprising: a tuner configured to receive a broadcast signal comprising data groups, each data group including enhanced data and known data sequences, wherein at least two of the known data sequences are spaced 16 segments apart; a demodulator configured to demodulate the received broadcast signal; a channel equalizer configured to compensate channel distortions of the demodulated broadcast signal based on channel impulse responses (CIRs) estimated using at least two of the known data sequences, wherein at least one CIR for enhanced data placed between the known data sequences is obtained by interpolating at least two of the estimated CIRs, and wherein at least one CIR for enhanced data not placed between the known data sequences is obtained by extrapolating at least two of the estimated CIRs; a block decoder configured to decode the enhanced data in the channel distortion compensated broadcast signal; a Reed-Solomon (RS) frame decoder configured to correct errors in the enhanced data based on a number of errors estimated by performing Cyclic Redundancy Check (CRC) decoding on an RS frame and a reliability map representing reliability information of the enhanced data, wherein the RS frame comprises K number of packets having A bytes of enhanced data, RS parity data generated based on the K number of packets, and CRC checksum data generated based on the K number of packets having the RS parity data, wherein K>1 and A>1; and a derandomizer configured to derandomize the error-corrected enhanced data.

2. The receiving system of claim 1 , wherein each data group comprises a plurality of regions, wherein the enhanced data included in at least one region of the plurality of regions are encoded at a coding rate of 1/X and the enhanced data included in at least another region of the plurality of regions are encoded at a coding rate of 1/Y, wherein X and Y are not same.

3. The receiving system of claim 2 , wherein a value of X is equal to 2, and a value of Y is equal to 4.

4. The receiving system of claim 1 , wherein, if the number of errors indicated on an error flag corresponding to each row within the RS frame by performing the CRC decoding is equal to or smaller than a number of the RS parity data added in a column direction of the RS frame, the second decoder performs RS eraser decoding on all columns of the RS frame in the column direction.

5. The receiving system of claim 1 , wherein, if the number of errors indicated on an error flag corresponding to each row within the RS frame by performing the CRC decoding is greater than a number of the RS parity data added in a column direction of the RS frame, the second decoder determines for each column either general RS decoding or RS erase decoding based upon the reliability map and then performs error correction by using the error correction decoding method determined for each corresponding column.

6. The receiving system of claim 5 , wherein, if a number of the enhanced data indicated as not reliable in the corresponding column of the reliability map is equal to or smaller than the number of the RS parity data added in the corresponding column, the second decoder performs the RS eraser decoding on the column, otherwise the second decoder performs the general RS decoding on the column.

7. A receiving method, comprising: receiving a broadcast signal comprising data groups, each data group including enhanced data and known data sequences, wherein at least two of the known data sequences are spaced 16 segments apart; demodulating, by a demodulator, the received broadcast signal; compensating channel distortions of the demodulated broadcast signal based on channel impulse responses (CIRs) estimated using at least two of the known data sequences, wherein at least one CIR for enhanced data placed between the known data sequences is obtained by interpolating at least two of the estimated CIRs, and wherein at least one CIR for enhanced data not placed between the known data sequences is obtained by extrapolating at least two of the estimated CIRs; decoding, by a block decoder, the enhanced data in the channel distortion compensated broadcast signal; correcting, by a Reed-Solomon (RS) decoder, errors in the enhanced data based on a number of errors estimated by performing Cyclic Redundancy Check (CRC) decoding on an RS frame and a reliability map representing reliability information of the enhanced data, wherein the RS frame comprises K number of packets having A bytes of enhanced data, RS parity data generated based on the K number of packets, and CRC checksum data generated based on the K number of packets having the RS parity data, wherein K>1 and A>1; and derandomizing, by a derandomizer, the error-corrected enhanced data.

8. The method of claim 7 , wherein each data group comprises a plurality of regions, wherein the enhanced data included in at least one region of the plurality of regions are encoded at a coding rate of 1/X and the enhanced data included in at least another region of the plurality of regions are encoded at a coding rate of 1/Y, wherein X and Y are not same.

9. The method of claim 8 , wherein a value of X is equal to 2, and a value of Y is equal to 4.

10. The method of claim 7 , wherein, if the number of errors indicated on an error flag corresponding to each row within the RS frame by performing the CRC decoding is equal to or smaller than a number of the RS parity data added in a column direction of the RS frame, RS eraser decoding is performed on all columns of the RS frame in the column direction.

11. The method of claim 7 , wherein, if the number of errors indicated on an error flag corresponding to each row within the RS frame by performing the CRC decoding is greater than a number of the RS parity data added in a column direction of the RS frame, either general RS decoding or RS erase decoding is determined for each column based upon the reliability map and then error correction is performed by using the error correction decoding method determined for each corresponding column.

12. The method of claim 11 , wherein, if a number of the enhanced data indicated as not reliable in the corresponding column of the reliability map is equal to or smaller than the number of the RS parity data added in the corresponding column, the RS eraser decoding is performed on the column, otherwise the general RS decoding is performed on the column.